Stabilized lithium metal powder for li-ion application, composition and process

ABSTRACT

The present invention provides a lithium metal powder protected by a wax. The resulting lithium metal powder has improved stability and improved storage life.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application Ser.No. 60/829,378, filed Oct. 13, 2006, the disclosure of which isincorporated by reference in its entirety.

FIELD OF INVENTION

The present invention relates to stabilized lithium metal powder(“SLMP”) having better stability and a longer storage life. Suchimproved SLMP can be used in a wide variety of applications includingorgano-metal and polymer synthesis, rechargeable lithium batteries, andrechargeable lithium ion batteries.

BACKGROUND OF THE INVENTION

The high surface area of lithium metal can be a deterrent for its use ina variety of applications because of its pyrophoric nature. It is knownto stabilize lithium metal powder by passivating the metal powdersurface with CO₂ such as described in U.S. Pat. Nos. 5,567,474,5,776,369, and 5,976,403, the disclosures of which are incorporatedherein in their entireties by reference. The CO₂-passivated lithiummetal powder, however, can be used only in air with low moisture levelsfor a limited period of time before the lithium metal content decaysbecause of the reaction of the lithium metal and air. Thus there remainsa need for stable lithium metal with an improved storage life.

SUMMARY OF THE INVENTION

The present invention provides a lithium metal powder protected by awax. A continuous wax layer provides improved protection such ascompared to, for example, CO₂ passivation. The resulting lithium metalpowder has improved stability and improved storage life. Furthermore,the wax-protected lithium metal powder exhibits better stability inN-methyl-2-pyrrolidone (NMP), which is widely used as a solvent in theelectrode fabrication process in the rechargeable lithium-ion batteryindustry. Similarly, the wax-protected lithium metal powder of theinvention exhibits better stability in gamma-butyrolactone (GBL).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a stability comparison of the wax-coated lithium metal powderof Example 1 and a CO₂-stabilized lithium metal powder in dry NMP.

FIG. 2 is a comparison of the cycle performance of graphite electrodewith wax as an additive and without wax additive.

FIG. 3 is a side-by-side comparison of ARSST stability test temperatureprofiles for the wax-coated lithium metal powder and of CO₂-coatedlithium metal powder in 0.6 percent water-doped NMP.

FIG. 4 is a stability comparison of Example 1 and CO₂-stabilized lithiummetal powder in 0.6 percent water-doped NMP.

FIG. 5 is an accelerated hygroscopisity tested conducted at 25° C. and75 percent relative humidity for NMP and GBL.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings and the following detailed description, preferredembodiments are described in detail to enable practice of the invention.Although the invention is described with reference to these specificembodiments, it will be understood that the invention is not limited tothese embodiments. But to the contrary, the invention includes numerousalternatives, modifications and equivalents as will become apparent fromconsideration of the following detailed description and accompanyingdrawing.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items. As used herein, the singularforms “a”, “an,” and “the” are intended to include the plural forms aswell, unless the context clearly indicates otherwise. It will be furtherunderstood that the terms “comprises” and/or “comprising,” when used inthis specification, specify the presence of stated features, integers,steps, operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein

In accordance with the present invention, lithium dispersions areprepared by heating the lithium metal powder in a hydrocarbon oil to atemperature above its melting point, subjecting the lithium metal powderto conditions sufficient to disperse the molten lithium (e.g., agitatingor stirring vigorously), and contacting the dispersed lithium metalpowder with a wax at a temperature that is between this temperature andthe melting point of the wax. Other alkali metals such as sodium andpotassium can be coated according to the present invention.

A variety of hydrocarbon oils may be used in the present invention. Theterm hydrocarbon oil, as used herein, includes various oily liquidsconsisting chiefly or wholly of mixtures of hydrocarbons and includesmineral oils, i.e., liquid products of mineral origin having viscositylimits recognized for oils and hence includes but is not limited topetroleum, shale oils, paraffin oils and the like. There are manymanufacturers of these useful hydrocarbon oils. Among these usefulhydrocarbon oils are highly refined oils, such as, Peneteck manufacturedby Penreco Division of Pennzoil Products Inc., which has a viscosity inthe range of 43-59 pascal-sec at 100° F. and a flash point of 265° F.,Parol 100, which has a viscosity of 213-236 pascal-sec at 100° F. and aflash point of 360° F. (available from Penreco, Div. of PennzoilProducts), and Carnation white oil (viscosity=133-165 pascal-sec at 100°F.) made by Sonneborn Div. of Witco. Even certain purified hydrocarbonsolvents which boil in a range encompassing the melting point of lithiumor sodium metal may be used, such as UNOCAL's 140 Solvent. In addition,unrefined oils, such as Unocal's 460 Solvent and Hydrocarbon Seal oiland Exxon's Telura 401 and Telura 407 may also be used. The selection ofa hydrocarbon oil will be within the skill of one in the art.

Suitable waxes can be natural wax such as 12-hydroxystearic acid,synthetic wax such as low molecular weight polyethylene, petroleum waxessuch as paraffin wax, and microcrystalline waxes. The wax can beintroduced to contact the lithium droplets during the dispersion, or ata lower temperature after the lithium dispersion has cooled. It isunderstood that combinations of different types of waxes with differentchemical compositions, molecular weights, melting points and hardnesscould be used to achieve specific coating characteristics for particularapplications. For example, degree of stickiness could be controlled toallow introduction of the SLMP using a “transfer release paper” concept,wherein a certain degree of stickiness is required.

Furthermore, it is beneficial to combine the wax or wax mixtures of theinvention with other inorganic coatings, for example, Li₂CO₃, LiF,Li₃PO₄, SiO₂, Li₄SiO₄, LiAlO₂, Li₂TiO₃, LiNbO₃ and the like, to improveboth air stability and polar solvent stability that would allow bothsafer handling and possibility of using commonly used polar solventsthat dissolve commonly used polymer binders. It is recognized that mostwaxes are soluble in non-polar solvents at elevated temperatures andsolubility at room temperature is above 0.5%. For example, wax issoluble in NMP at room temperature at about 0.1% level.

Suitable waxes described above could produce two types of coatings onlithium particles: first type representing physical or adhesive typewhere non-polar waxes are used and a second type, representingchemically bonded coatings where waxes with functional groups, havingboth hydrophobic and hydrophilic features, are used. The coatingthickness could vary in the range of about 20 nm to about 200 nm.

By altering the process parameters and the order of the reagentsaddition to the lithium dispersion or lithium dry powder, the wax-coatedlithium metal powder of the invention can have distinct surfaceproperties. For example, waxes could be introduced at or below meltingpoint of lithium followed by the addition of other dispersants above themelting point of lithium, and, therefore, the wax serves asdispersant/coating reagents. Other suitable dispersants include oleicacid, linoleic acid, sodium oleate, lithium oleate, linseed oil, CO₂,N₂, NH₃, telura oil, stearic acid, oxalic acid, tanic acid, CO, andother waxes. Waxes or wax mixtures could be introduced above the meltingpoint of lithium before or after other dispersants and coating reagentsadditions, for example the reagents that result in formation of thecoatings such as Li₂CO₃, LiF, Li₃PO₄, SiO₂, Li₄SiO₄, LiAlO₂, Li₂TiO₃,and LiNbO₃, and the like, to enhance the chemical bonding and uniformityof protecting layer by changing the reaction interfaces. The coolingprofile could be used to control degree of crystallinity and obtainsamples with pre-determined degree of stickiness.

Alternatively, stabilized lithium metal powder could be dispersed intothe melted non-polar paraffin-like waxes or a mixture of waxes, andpoured into the candle type mold for crystallization and theconcentration of lithium powder could be calculated as a function oflength or volume. Consequently, a piece of a “candle” could serve as alithium carrier and used for organo-metallic and or polymer syntheses;the inert wax could be extracted with a solvent or allowed tocrystallize out and filtered out upon reaction completion.

In another embodiment, stabilized lithium metal powder could bedispersed into the melted non-polar paraffin-like waxes or a mixture ofwaxes with mineral oil to form a lithium powder containing slurry orpaste that could be used in a caulk-gun like apparatus for lithiumpowder delivery.

The process produces lithium dispersions having metal particle sizes inthe range of 10 to 500 microns. Moreover, the tendency of the lithiumparticles to float to the top of the slurry is obviated by practice ofthe present invention. It is recognized that one skilled in the art willbe able to choose the appropriate particle size depending on theintended use of the lithium dispersion. On cooling, the resultinglithium dispersions are readily filtered to remove the bulk of thedispersant hydrocarbon oil and the metal can then be washed with asolvent such as hexane to remove residual oil, after which, the metalpowder can be dried. The hydrocarbon oil filtrate is clear and colorlessand may be recycled, without further treatment, to the metal dispersionprocess. This is in contrast to the prior art processes which requireclay column purification of the oil before reuse. The dried metalpowders are unexpectedly stable to ambient atmosphere allowing theirsafe transfer in such atmospheres from one container to another.

Lithium metal used with various embodiments of the present invention maybe provided as lithium powder. The lithium powder may be treated orotherwise conditioned for stability during transportation. For instance,dry lithium powder may be formed in the presence of carbon dioxide asconventionally known. It may be packaged under an inert atmosphere suchas argon. The dry lithium powder may be used with the variousembodiments of the present invention. Alternatively, the lithium powdermay be formed in a suspension, such as in a suspension of mineral oilsolution or other solvents. Formation of lithium powder in a solventsuspension may facilitate the production of smaller lithium metalparticles, for example, wherein 100 percent of particles are less than100 micron. In some embodiments of the present invention, a lithiumpowder may be formed in a solvent that may be used with variousembodiments of the present invention. The lithium metal powder formed inthe solvent may be transported in the solvent. Further, the lithiummetal powder and solvent mixture may be used with embodiments of thepresent invention, wherein the step of drying SLMP is eliminated. Thismay decrease production costs and allow the use of smaller or finerlithium metal powder particles with the embodiments of the presentinvention.

Alternatively the stabilized lithium metal powder can be produced byspraying the molten metal through an atomizer nozzle, and the waxingstep can take place after the powder has been collected. For example,lithium powder could be collected into lithium compatible solventcontaining dry wax or pre-dissolved wax and the mixture brought to orabove the temperature of the clear point of wax in the solvent, and inone embodiment above the melting point of lithium. The solvent can bestripped away, using rotary evaporator, as an example, causing wax tocrystallize onto the lithium particles. Solvents used with embodimentsof the invention must also be non-reactive with the lithium metal andthe binder polymers (binders could be soluble in the solvents compatiblewith lithium) at the temperatures used in the anode production process.Preferably, a solvent or co-solvent possesses sufficient volatility toreadily evaporate from a slurry to promote the drying of a slurryapplied to a current collector. For example, solvents may includeacyclic hydrocarbons and cyclic hydrocarbons including NMP, GBL,n-hexane, n-heptane, cyclohexane, and the like, aromatic hydrocarbons,such as toluene, xylene, isopropylbenzene (cumene), and the likesymmetrical, unsymmetrical, and cyclic ethers, including di-n-butylether, methyl t-butyl ether, and the like.

In one embodiment, the lithium metal powder protected with wax coatingenables the use of dry NMP solvent.

The stabilized lithium metal powder can be used in a secondary batterysuch as described in U.S. Pat. No. 6,706,447 B2, the disclosure of whichis incorporated by reference in its entirety. A typical secondarybattery comprises a positive electrode or cathode, a negative electrodeor anode, a separator for separating the positive electrode and thenegative electrode, and an electrolyte in electrochemical communicationwith the positive electrode and the negative electrode. The secondarybattery also includes a current collector that is in electrical contactwith the cathode and a current collector that is in electrical contactwith the anode. The current collectors are in electrical contact withone another through an external circuit. The secondary battery can haveany construction known in the art such as a “jelly roll” or stackedconstruction.

The cathode is formed of an active material, which is typically combinedwith a carbonaceous material and a binder polymer. The active materialused in the cathode is preferably a material that can be lithiated at auseful voltage (e.g., 2.0 to 5.0 V versus lithium). Preferably,non-lithiated materials such as MnO₂, V₂O₅ or MoS₂, certain transitionmetal phosphates, certain transition metal fluorides, or mixturesthereof, can be used as the active material. However, lithiatedmaterials such as LiMn₂O₄ that can be further lithiated can also beused. The non-lithiated active materials are selected because theygenerally have higher specific capacities, better safety, lower cost andbroader choice than the lithiated active materials in this constructionand thus can provide increased power over secondary batteries that useonly lithiated active materials. Furthermore, because the anode includeslithium as discussed below, it is not necessary that the cathodeincludes a lithiated material for the secondary battery to operate. Theamount of active material provided in the cathode is preferablysufficient to accept the removable lithium metal present in the anode.

The anode is formed of a host material capable of absorbing anddesorbing lithium in an electrochemical system with the stabilizedlithium metal powder dispersed in the host material. For example, thelithium present in the anode can intercalate in, alloy with or beabsorbed by the host material when the battery (and particularly theanode) is recharged. The host material includes materials capable ofabsorbing and desorbing lithium in an electrochemical system such ascarbonaceous materials; materials containing Si, Sn, tin and siliconoxides or composite tin and or silicon alloys or intermetallics;transition metal oxides such as cobalt oxide; lithium metal nitridessuch as Li_(3-x)Co_(x)N where 0<x<0.5, and lithium metal oxides such asLi₄Ti₅O₁₂.

An alternative use of the stabilized lithium metal powder is in thepreparation of organo lithium products in good yields. The thin waxlayer is believed to not significantly retard reactivity but doesprotect the metal from reaction with ambient atmosphere.

The following examples are merely illustrative of the invention, and arenot limiting thereon.

EXAMPLES Comparative Example 1

Battery grade lithium metal 405 grams was cut into 2×2 inch pieces andcharged under constant flow of dry argon at room temperature to a 3liter stainless steel flask reactor with a 4″ top fitted with a stirringshaft connected to a fixed high speed stirrer motor. The reactor wasequipped with top and bottom heating mantles. The reactor was thenassembled and 1041.4 g of Peneteck™ oil (Penreco, Division of thePenzoil Products Company) was added. The reactor was then heated toabout 200° C. and gentle stirring was maintained in the range of 250 rpmto 800 rpm to ensure all metal was molten, argon flow was maintainedthrough out the heating step. Then the mixture was stirred at high speed(up to 10,000 rpm) for 2 minutes. Oleic acid, 8.1 g was charged into thereactor and high speed stirring continued for another 3 minutes followedby the 5.1 g CO₂ addition. Then the high speed stirring was stopped,heating mantles removed and dispersion was allowed to cool to about 50°C. and transferred to the storage bottles. Further, lithium dispersionwas filtered and washed three times with hexane and once with n-pentanein an enclosed, sintered glass filter funnel to remove the hydrocarbonoil medium while under argon flow. The funnel was heated with a heat gunto remove traces of the solvents and the resulting free-flowing powderwas transferred to a tightly capped storage bottles.

Example 1

Lithium dispersion in oil, 55.72 grams, (11.275%) containing 6.28 gramsof lithium with a medium particle size of 58 micron was charged into 120ml hastelloy can equipped with a 1″ Teflon coated stir bar. The solutionwas heated to 75° C. and 0.63 grams of Luwax A (BASF) in a form of 10%solution in p-xylene (Aldrich) pre-dissolved at 72° C. was added to thelithium dispersion. This mixture was continuously stirred at 200 rpm for22 hours. Sample was allowed to cool to the room temperature andtransferred to the storage bottle. Further, lithium dispersion wasfiltered and washed three times with hexane in an enclosed, sinteredglass filter funnel and twice with n-pentane to remove the hydrocarbonoil medium. The funnel was heated with a heat gun to remove traces ofthe solvents and the resulting free-flowing powder was transferred to atightly capped storage bottles.

FIG. 1 shows that no exothermic effects were observed when Example 1 wasmixed at room temperature in dry NMP (<100 ppm H₂O). Moreover, unlikesample described in Comparative Example 1 that had no metallic lithiumleft after four days of exposure to dry NMP solvent, 54 percent metalliclithium was still present in Example 1. Furthermore, unlike sampledescribed in Comparative Example 1, wax-coated lithium powder is evenstable with NMP with the amount of moisture of 0.6 percent. FIG. 2illustrates that when 1 wt % wax is introduced into the battery,(addition is calculated based on a fully lithiated carbon using 10%wax-coated SLMP) there are no adverse effects. Half cells of Li/Carbonwere tested using Arbin battery cycler BT-2043. The cells were cycled at0.50 mA/cm² with a potential window of 0.01˜1.5 V.

FIG. 3 shows an ARSST (advanced reactive screening system tool)calorimeter test where samples were exposed to the 0.6 percent waterdoped NMP under continuous stirring and three days isothermal hold atroom temperature was followed by the 2 days isothermal hold at 55° C.Runaway reaction was observed for the CO₂-coated lithium powder at about48 hours of hold at room temperature while no exothermic effect wasobserved for the wax-coated lithium metal powder of Example 1. Uponcompletion of these types of tests, the lithium metallic concentrationfor the wax-coated samples is at least 40 percent. FIG. 4 shows themetallic lithium concentration measured for the wax-coated samplefollowed by their exposure to the 0.6 percent water doped NMP over theperiod of 10 days at room temperature.

Solvent hygroscopisity causes quality and performance issues for theLi-ion batteries (for example, high moisture content might cause binderpolymer to re-crystallize, thus reducing its binding properties, thuscausing electrode film to crack, delaminate, thus causing failure of thebattery). FIG. 5 shows accelerated hygroscopicity test results conductedat 25° C. and 75 percent relative humidity. For example, while NMPabsorbs ˜0.6 percent of moisture within 7 hours of exposure, GBL absorbsonly 0.23 percent of moisture. This shows that the wax-coated lithiummetal powder is even more stable in GBL.

Example 2

Lithium dispersion in oil, 780 g, (32.1%) that contained 250 g oflithium with a medium particle size of 63 micron was charged underconstant flow of dry argon at room temperature to a 5 liter three neckglass flask reactor fitted with a stirring shaft connected to a fixedhigh speed stirrer motor. The reactor was equipped with bottom heatingmantles. The reactor was then heated to about 75° C. and gentle stirringwas maintained to ensure uniform distribution and heat transfer. 25 g ofLuwax A (BASF) in a form of a 10% solution pre-dissolved in p-xylene at72° C. was charged into the reactor and stirring continued for another 8hours. The solution was then cooled slowly and kept at room temperaturewhile being further stirred for 14 hrs and then transferred to thestorage bottles. Further, lithium dispersion was filtered and washedthree times with hexane in an enclosed, sintered glass filter funnel andtwice with n-pentane to remove the hydrocarbon oil medium. The funnelwas heated with a heat gun to remove traces of the solvents and theresulting free-flowing powder was transferred to a tightly cappedstorage bottles.

A pyrophoricity test (Method 1050 of DOT regulations for the transportof spontaneously combustible materials, Code of Federal Regulations part173, Appendix E) performed on this material showed it to benon-pyrophoric.

Example 3

Lithium dispersion in mineral oil 21.45 grams (27.5%) that contained5.90 g of lithium and had medium particle size of 63 microns and 0.62 gLuwax A powder were charged under constant flow of dry argon at roomtemperature to a 125 ml glass flask reactor with a magnetic stirrer barcontrolled by super magnetic stirrer. The reactor was equipped withbottom heating mantle. The reactor was then heated to the temperaturerange of 90° C. to 100° C. and stirring was maintained at ˜400 rpm toensure uniform distribution and heat transfer for a period of about 1hour followed by a natural cooling.

Example 4

Lithium dispersion in mineral oil 21.56 grams (27.5%) that contained5.93 g of lithium and had medium particle size of 63 microns and 0.61 gLuwax A powder were charged under constant flow of dry argon at roomtemperature to a 125 ml glass flask reactor with a magnetic stirrer barcontrolled by super magnetic stirrer. Gentle stirring was maintained ˜50rpm to ensure uniform distribution and heat transfer before temperaturewas increased to 90° C. The reactor was equipped with bottom heatingmantle. The reactor was then heated to the temperature range of 90° C.to 100° C. and then the stirring was increased to ˜200 rpm, and themixture was kept under stirring for about 15 minutes. Then, the heatingmantle was taken off and the reactor was allowed to cool naturally.

Example 5

Lithium dispersion in mineral oil, 21.72 grams (27.5%) that contained5.97 g of lithium and had medium particle size of 63 microns was chargedunder constant flow of dry argon at room temperature to a 125 ml glassflask reactor with a magnetic stirrer bar controlled by super magneticstirrer. Gentle stirring was maintained at ˜30 rpm to ensure uniformdistribution and heat transfer before temperature was increased to 90°C. The reactor was equipped with bottom heating mantle. After thereactor was heated to the temperature of 90° C., 6.55 g (10%)pre-dissolved Luwax A solution in mineral oil was charged into thereactor and the stirring increased to 200 rpm. Then the mixture was keptunder stirring for about 15 minutes followed by natural cooling.

Example 6

Lithium dispersion in mineral oil, stabilized with the CO₂-gas, 22.30grams, (27.5%) that contained 6.13 g of lithium with medium particlesize of 45 microns was charged under constant flow of dry argon at roomtemperature to a 125 ml glass flask reactor with a magnetic stirrer barcontrolled by super magnetic stirrer. Gentle stirring was maintained ˜30rpm to ensure uniform distribution and heat transfer before temperatureincreased to 90° C. The reactor was equipped with bottom heating mantle.After the reactor was heated to the temperature of 90° C., 6.52 gpre-dissolved 10% Luwax A solution in mineral oil was charged into thereactor and the stirring increased to ˜200 rpm. Then the mixture waskept under stirring for about 15 minutes followed by the naturalcooling.

Example 7

5 g of dry stabilized lithium metal powder (LectroMax Powder 150, FMC),75 g p-xylene (Aldrich) and 0.1 g Luwax A powder (BASF) were chargedunder constant flow of dry argon at room temperature to a 200 ml threeneck glass flask reactor fitted with a stirring shaft connected to afixed high speed stirrer motor. The reactor was equipped with bottomheating mantles. The reactor was then heated to about 75° C. and gentlestirring was maintained to ensure uniform distribution and heattransfer. The mixture was stirred for 20 minutes at 75° C. and theheating mantle was then removed to allow the sample to cool rapidly.Further, mixture was filtered in an enclosed, sintered glass filterfunnel. The sample was dried by passing dry argon through the filter.The resulting free-flowing powder was transferred to a tightly cappedstorage bottles.

Example 8

Dry stabilized lithium metal powder, 10 g, (LectroMax Powder 150, FMC),50 g p-xylene (Aldrich) and 0.5 g Luwax A powder (BASF) were charged inan argon filled glove box at room temperature to a 250 ml round bottomflask. The flask was then attached to a rotary vacuum solvent extractor(Buchi Rotavapor R110) and partially submerged in a mineral oil bath atroom temperature. The flask was turned while the mineral oil bath washeated to 80° C. The temperature of the mixture was maintained at 80° C.with no vacuum applied for 30 minutes. A vacuum of 25 inches of Hg wasthen applied to strip the p-xylene. After 50% of the solvent wasremoved, the flask was raised out of the oil bath and allowed to coolrapidly. The remaining solvent was filtered in an enclosed, sinteredglass filter funnel. The sample was dried by passing dry argon throughthe filter. The resulting free-flowing powder was transferred to atightly capped storage bottles.

Example 9

4924 g of mineral oil and 1364 g of battery grade lithium metal rodswere added to an argon inerted 5 gallon dispersion apparatus. Themixture was heated to temperature above lithium melting point under anargon atmosphere with stirring to ensure that all lithium has melted.The high speed disperser blade was then started and a mixture of 27 g ofoleic acid and 29 g of mineral oil was introduced into the dispersionpot. After an additional several minutes of high speed stirring, 18 g ofCO₂ carbon dioxide gas was introduced. After this, the high speedstirring was brought down to minimum speed and reaction mixture cooleddown to 105° C. with external cooling. 136 g of Luwax A powder (BASF)was introduced and the temperature was maintained above 95° C. for thenext 15 minutes followed by cooling to ambient temperature. The waxcoated SLMP dispersion was then transferred out of the pot. A sample ofthe dispersion was washed with hexane and pentane to remove the mineraloil. The material was then dried under argon.

Example 10

Dry stabilized lithium metal powder, 10 g, (LectroMax Powder 150, FMC),50 g p-xylene (Aldrich) and 0.5 g Luwax A powder (BASF) were charged inan argon filled glove box at room temperature to a 250 ml round bottomflask. The flask was then attached to a rotary vacuum solvent extractor(Buchi Rotavapor R110) and partially submerged in a mineral oil bath atroom temperature. The flask was turned while the mineral oil bath washeated to 80° C. The temperature of the mixture was maintained at 80° C.with no vacuum applied for 30 minutes. A vacuum of 25 inches of Hg wasthen applied to strip the p-xylene. As the sample began to dry thevacuum was lowered to 30 inches of Hg to remove the remaining solvent.The flask was removed from the rotary evaporator and the sample wasfurther dried by passing dry argon through the flask. The resultingpowder was transferred to a tightly capped storage bottles.

Example 11

Battery grade lithium metal 4427 g and 15345 g of mineral oil were addedto a 15 gallon dispersion pot. The mixture was heated to the temperatureabove the melting point of lithium metal while stirring. Then the highspeed disperser blade was set into motion at 4800 rpm and a mixture of90 gm of oleic acid and 90 g of mineral oil was introduced in to thedispersion pot. After several minutes of high speed dispersion, 58 g ofcarbon dioxide gas was introduced in to the pot and allowed to reactwith the metal particles. The high speed disperser was shut off shortlyafter CO₂ addition and cold mineral oil was added to the mix to bringthe temperature of the dispersion below the melting point of lithiummetal. Anchor agitator was used to continue stirring the dispersionmixture until the material was cooled down to the room temperature topromote uniformity of the suspension. External cooling was applied tothe system. The material was discharged and analyzed. The mean diameterof the stabilized lithium dispersion was 52 micron.

Example 12

Battery grade lithium metal 44137 g and 15436 g of mineral oil wereadded to a 15 gallon dispersion pot. The mixture was heated to thetemperature above the melting point of lithium metal under continuousstirring. Then the high speed disperser blade was set into motion at4800 rpm and a mixture of 89 gm of oleic acid and 87 g of mineral oilwas introduced into the dispersion pot. After several minutes of highspeed dispersion, 57 g of carbon dioxide gas was charged into the potand allowed to react with the metal particles. Upon completion of thereaction, 118 g of Luwax S was introduced into the pot. After additionalhigh speed mixing the high speed disperser was shut off and cold mineraloil was added to the mix to bring the temperature below the meltingpoint of lithium metal. Anchor agitator was used to continue stirringthe dispersion mixture until the material was cooled down to the roomtemperature to promote uniformity of the suspension. External coolingwas applied to the system. The material was discharged and analyzed. Themean diameter of the stabilized lithium dispersion was 40 micron.

These two examples and figures demonstrate that wax could be used bothas a coating reagent and as a dispersant reagent. This is a veryimportant property that could be used in designing products with reducedparticle size/increased surface area for specific applications, forexample spraying SLMP powder in the solvent solution onto the electrodesurfaces or continuously introducing dry SLMP powder into the Tokamakedge using the “gun”-like devices to increase plasma stability andelectron temperatures and reduce the impurity levels (lithium is agetter). Table 1 below summarizes specific process conditions andparticle size results.

TABLE 1 Process conditions and experimental results for examples 11 and12 Oleic Dispersing Stabilizing D50 acid, % Speed RPM Additives micronExample 11 2% 4800 1.25% CO2 52 Example 12 2% 4800 1.25% CO2 & 2.5% 40Luwax S

Having thus described certain embodiments of the present invention, itis to be understood that the invention defined by the appended claims isnot to be limited by particular details set forth in the abovedescription as many apparent variations thereof are possible withoutdeparting from the spirit or scope thereof as hereinafter claimed. Thefollowing claims are provided to ensure that the present applicationmeets all statutory requirements as a priority application in alljurisdictions and shall not be construed as setting forth the full scopeof the present invention.

1. A stabilized lithium metal powder coated with a wax.
 2. Thestabilized lithium metal powder of claim 1, wherein the wax has athickness of 20 μm to 200 μm.
 3. The stabilized lithium metal powder ofclaim 2, wherein the wax is selected from the group consisting ofnatural waxes, synthetic waxes, petroleum waxes, and microcrystallinewaxes.
 4. The stabilized lithium metal powder of claim 3, furthercomprising an inorganic coating.
 5. The stabilized lithium metal powderof claim 4, wherein the inorganic coating is selected from the groupconsisting of Li₂CO₃, LiF, Li₃PO₄, SiO₂, Li₄SiO₄, LiAlO₂, Li₂TiO₃, andLiNbO₃.
 6. An anode comprising a host material capable of absorbing ordesorbing lithium in an electrochemical system wherein the stabilizedlithium metal of claim 1 is dispersed in the host material.
 7. An anodecomprising a host material capable of absorbing or desorbing lithium inan electrochemical system wherein the stabilized lithium metal of claim3 is dispersed in the host material.
 8. The anode of claim 6, whereinsaid host material comprises at least one material selected from thegroup consisting of carbonaceous materials, silicon, tin, tin oxides,composite tin alloys, transition metal oxides, lithium metal nitrides,graphite, carbon black, and lithium metal oxides.
 9. The anode of claim7, wherein said host material comprises at least one material selectedfrom the group consisting of carbonaceous materials, silicon, tin, tinoxides, composite tin alloys, transition metal oxides, lithium metalnitrides, graphite, carbon black, and lithium metal oxides.
 10. Thestabilized lithium metal powder according to claim 1, wherein saidpowder has a mean diameter of from 10 μm to 200 μm inN-methyl-2-pyrrolidone.
 11. The stabilized lithium metal powderaccording to claim 1, wherein said powder has a mean diameter of from 10μm to 200 μm in gamma-butyrolactone.
 12. A method of forming a lithiumdispersion comprising the steps of: a) contacting lithium metal powderwith a hydrocarbon oil; b) heating the lithium metal powder andhydrocarbon oil to a temperature higher than the melting point of thelithium metal powder; c) subjecting the heated lithium metal powder andhydrocarbon oil to conditions sufficient to disperse the lithium metalpowder in the oil; and d) contacting the lithium metal powder with a waxat a temperature between the melting point of the lithium metal powderand the melting point of the wax.
 13. The method of claim 12, whereinthe wax has a thickness of 20 nm to 200 nm.
 14. The method of claim 12,wherein the hydrocarbon oil is selected from the group consisting ofpetroleum oils, shale oils, and paraffin oils.
 15. A method of forming alithium dispersion comprising the steps of: a) contacting lithium metalpowder with a hydrocarbon oil; b) heating the lithium metal powder andhydrocarbon oil to a temperature higher than the melting point of thelithium metal powder; c) adding a dispersant and a coating reagent; d)subjecting the heated lithium metal powder and hydrocarbon oil toconditions sufficient to disperse the lithium metal powder in the oil;and e) contacting the lithium metal powder with a wax at a temperaturebetween the melting point of the lithium metal powder and the meltingpoint of the wax.
 16. The method of claim 15, wherein the wax has athickness of 20 nm to 200 nm.
 17. The method of claim 15, furthercomprising an inorganic coating.